Pathophysiology
1) cause is infection with Francisella tularensis 2) occurs in more serious type A and less serious type B variants 3) specific clinical forms – ulceroglandular, oculoglandular, oropharyngeal, typhoidal, and pulmonary
Signs and Symptoms
1) symptoms occur 2-5 days after introduction of organism into a human Ulceroglandular form – 2) first sign is tender papule with characteristic pustular ulcer with a black base that progresses to regional adenitis in 2-3 days 3) followed by abrupt onset of flu-like illness (fever, chills, drenching sweats, headache, myalgias) Oculoglandular form – 4) keratitis 5) uveitis 6) conjunctivitis 7) preauricular lymphadenopathy Oropharyngeal form – 8) pharyngitis 9) cervical lymphadenopathy Typhoidal form – 10) abdominal pain 11) vomiting 12) diarrhea 13) gastrointestinal bleeding Pulmonary form – 14) pneumonia 15) nonproductive cough
Characteristic Test Findings
Chest radiograph – 1) bilateral patchy infiltrates/lobar infiltrate Laboratory – 2) leuckocytosis/left shift 3) diagnosis is via serology: considered positive if any single titer is > 1:160 (30% specificity)
Histology/Gross Pathology
1) small, gram-negative, non-motile, aerobic bacillus 2) enlarged mesenteric lymph nodes 3) areas of focal necrosis in liver, spleen, lymph nodes, and skin
Associated Conditions
1) Parinaud’s oculoglandular syndrome 2) hepatitis 3) pericarditis 4) meningitis 5) peritonitis 6) osteomyelitis
Inheritance/Epidemiology
1) type A is found in rabbits and rodents and type B is found in aquatic animals 2) enters humans via inhalation, ingestion, inoculation, or contamination 3) most cases involved with skinning wild rabbits or via tick or tabanid fly bites 4) endemic in southeastern USA 5) mortality is 5-6% in untreated cases and virtually non-existent in treated cases 6) does not have human-to-human transmission but is highly infectious; workers in microbiology labs who handle the organism are at risk of infection 7) one attack usually confers immunity
Treatment
1) drug of choice is streptomycin IM every 12 h for 7-14 days 2) also effective is gentamicin used in combination with a third-generation cephalosporin 3) vaccination with live attenuated strains is possible.
Tips for USMLE
if a 34 year old man in Georgia was out hunting and pulled some ticks out of his right leg and 4 days later had a fever and chills, and then noticed swelling in his right groin and a sore with a black scab at the base on his right anterior thigh, think tularemia
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